Depends on a few things. Are you open taping or running , What is your budget? Do you want to do an incremental upgrade or invest in a top of the line rig where you don't feel the need to upgrade again.

Do you want to do an incremental upgrade or invest in a top of the line rig where you don't feel the need to upgrade again.

(that'll never happen...)

I was actually looking at a Studio Projects C4 Kit on ebay with omnis, cards, mounts, etc. all in a nice case - opening bid is 200.00, I think you can get it new for $350. Not to be confused with Behringer C4s. you'll need some way to power them.

Open, and great question about upgrading / going top of the line. Who knows...but for purposes of this question, I wouldn't want to spend more than $1000 total.

You should easily be able to do something for under a grand. I would look for a pair of full bodied mics, but be sure to take into account all the accessories you'd need like mounts, cables, stand, and a preamp for your D50 to go XLR > 1/8". Other people know much more about this stuff than I do though.

I know you just bought that D50, but if you wanted to dip your toes into doing 4 track matrices (matrixes?) something simple like the Roland R-26 would get you there (with XLR inputs and phantom power for the full bodied mics) fairly inexpensively. They come around here every so often. But again, others know better than me.

Do you want to do an incremental upgrade or invest in a top of the line rig where you don't feel the need to upgrade again.

(that'll never happen...)

I was actually looking at a Studio Projects C4 Kit on ebay with omnis, cards, mounts, etc. all in a nice case - opening bid is 200.00, I think you can get it new for $350. Not to be confused with Behringer C4s. you'll need some way to power them.

I only run and bought Schoeps MK4's in the early 90's. Have found no need to upgrade from there although I have since bought MK41's for a change of pace. The MK4's have done about 1000 shows

Mikes are the single biggest upgrade in the chain and pretty much anything will be an upgrade. How far you want to go depend on your budget. I'd start at AKG move up to Neumanns and if you got the scratch to Schoeps, of course.